System for actuating a laparoscopic surgical instrument

ABSTRACT

The invention is directed to a pin and slot design where the driving slots are moved from the tips to the actuation rod in one aspect of the invention. As a result, the back end of each blade or tip can be dramatically reduced in area so that during full deflection, very little or no part of the blade or tip extends beyond the outside diameter of the shaft. This ensures that nothing catches on the blades or tips during grasper use and the shrink tubing found on the scissors would not be deformed. This can be done because the area for the slots is not needed. Moreover, the usable area for the drive slots on the blade or tip of the actuation rod is maximized to the overall diameter of the outer tube or shaft which provides additional leverage to the blades or tips. In addition, the depth of each slot can be varied such that during actuation, increased tension can be put on the blades or tips throughout the cut. More specifically, the surgical instrument of the invention comprises an elongate tube extending along an axis including an actuation rod coaxially slidable within the elongate tube, a first tip including a first pin formed on a proximal end surface of the first tip, and a second tip including a second pin formed on a proximal end surface of the second tip, the second tip pivotally connected to the first tip at a common pivot pin operably connected to the elongate tube to open and close the tips in response to movement of the actuation rod. The actuation rod has a slot to accept the pins of the first and second tips, the slot has camming surfaces for the pins to slide within the slot, and the proximal ends of the tips extend minimally outside the diameter of the elongate tube during actuation of the tips.

This is a non-provisional application claiming the priority ofprovisional application Ser. No. 60/548,747, filed on Feb. 27, 2004,entitled “System and Method of Actuating a Laparoscopic SurgicalInstrument,” which is fully incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to laparoscopic surgical instrumentsand, in particular, to a system and method for actuating the tips of alaparoscopic surgical instrument.

2. Description of Prior Art

Laparoscopic surgical instruments or devices that use actuating bladesor tips are typically activated by some mechanical means. In most cases,the surgical instruments or devices use an actuation rod to translatemotion from a handle at one end to a tip at the opposite end of thedevice. Common to laparoscopic scissors and graspers is an actuation rodthat includes a pin that works in conjunction with a slot in the tips.Moving the actuation rod cams the pin in the slot which opens and closesthe tips.

The blades or tips typically have slots proximal to the pivot andbecause of this configuration, the back end of the blades or tips needto be quite large. When used on a grasper and the tips are in their openposition, the back end of the tips extend out beyond the outsidediameter of the grasper shaft and look like “wings.” This may be aproblem for the user and, in particular, the patient as they can catchor interfere on tissue or other devices during use.

When used on scissors, these wings will most likely be covered up with aplastic shrink tubing to insulate all the metal components duringelectro-surgical cautery. However, when the blades or tips are open, thewings can stretch and deform the shrink tubing. This can be problematicin that when the scissors is withdrawn from the trocar, the deformedtubing may not relax and it may catch on the end of the cannula, therebypulling the trocar out of the patient. Accordingly, there is a need inthe art for an improved system and method for actuating the blades ortips of laparoscopic instruments so as to minimize the adverse wingeffect.

SUMMARY OF THE INVENTION

The invention is directed to a pin and slot design where the drivingslots are moved from the blades or tips to the actuation rod in oneaspect of the invention. As a result, the back end of each blade or tipcan be dramatically reduced in area so that during full deflection, verylittle or no part of the blade or tip extends beyond the outsidediameter of the outer tube or shaft. This ensures that nothing catcheson the blades or tips during grasper use and the shrink tubing found onthe scissors would not be deformed. This can be done because the areafor the slots is not needed. Moreover, the usable area for the driveslots on the blade or tip of the actuation rod is maximized to theoverall diameter of the outer tube or shaft which provides additionalleverage to the blades or tips. In addition, the depth of the slot canbe varied such that increased tension can be placed on the blades ortips during actuation.

More specifically, the invention is directed to a surgical instrumentcomprising an elongate tube extending along an axis including anactuation rod coaxially slidable within the elongate tube, a first tipincluding a first pin formed on a proximal end surface of the first tip,and a second tip including a second pin formed on a proximal end surfaceof the second tip, the second tip pivotally connected to the first tipat a common pivot pin operably connected to the elongate tube to openand close the tips in response to movement of the actuation rod. Withthis aspect, the actuation rod has a slot to accept the pins of thefirst and second tips, the slot has camming surfaces for the pins toslide within the slot, and the proximal ends of the tips extendminimally outside the diameter of the elongate tube during actuation ofthe tips. In another aspect, the proximal ends of the tips do not extendoutside the diameter of the elongate tube during actuation of the tips.The actuation rod can be formed by machining, stamping, overmolding,casting, or metal injection molding. The pins can be formed on theproximal end surfaces of the tips by press fitting, threading, weldingor bonding. The actuation rod can be a tongue actuation rod or a forkactuation rod. With the fork actuation rod, the rod can include athrough slot on each side of the rod, which may be curved and transverseto one another. The tongue actuation rod can also include two curved andtransverse slots on opposing sides of the tongue. It is appreciated thatthe slots can be open-ended or closed-ended. As stated above, the slotmay have a depth that varies along the length of the slot. Inparticular, the different depth of the slot provides different tensionalong the tip. In another aspect, the tongue actuation rod includesmeans for ratcheting the tips into a desired position; the ratchetingmeans may include a series of detents.

In another aspect of the invention, there is disclosed a surgicalinstrument comprising an elongate tube extending along an axis includingan actuation rod coaxially operable within the elongate tube, a firsttip including a first cam slot with a first camming surface, and asecond tip including a second cam slot with a second camming surface,the second tip pivotally connected to the first tip at a common pivotpin operably connected to the elongate tube to open and close the tipsin response to movement of the actuation rod. With this aspect, theactuation rod includes a third slot to hold a floating drive pin, thefloating drive pin is placed through the first and second cam slots, andthe proximal ends of the tips extend minimally outside the diameter ofthe elongate tube during actuation of the tips. In another aspect, theproximal ends of the tips do not extend outside the diameter of theelongate tube during actuation of the tips. The third slot may be avertical slot and the elongate tube may further comprise a floatingdrive pin slot at the proximal portion of the tube.

In yet another aspect of the invention, there is disclosed a surgicalinstrument comprising a shaft assembly extending along an axis includinga rotatable outer shaft and a coaxial inner rod, a first tip including afirst pin formed on a proximal end surface of the first tip, and asecond tip including a second pin formed on a proximal end surface ofthe second tip, the second tip pivotally connected to the first tip at acommon pivot pin operably connected to the shaft assembly to open andclose the tips in response to movement of the outer shaft. With thisaspect, the outer shaft has a slot to accept the pins of the first andsecond tips, the slot has camming surfaces for the pins to slide withinthe slot, and the proximal ends of the tips extend minimally outside thediameter of the shaft assembly during actuation of the tips, which areactuated by rotating the outer shaft. In another aspect, the proximalends of the tips do not extend outside the diameter of the elongate tubeduring actuation of the tips.

These and other features and advantages of the invention will becomemore apparent with a discussion of the embodiments in reference to theassociated drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a laparoscopic view of asurgical instrument of the prior art;

FIG. 2 illustrates a side cutaway view of a tool mechanism of thesurgical instrument of FIG. 1 in the open position;

FIG. 3 is an exploded perspective view of FIG. 2;

FIGS. 4( a)-4(c) illustrate a perspective view of a laparoscopicsurgical instrument of the invention, a perspective view of a blade ortip of the tool mechanism of the invention, and a side view of FIG. 4(a), respectively;

FIG. 5 illustrates a perspective view of an assembled surgicalinstrument of the invention having mobile tips and an actuation rod;

FIGS. 6( a) and 6(b) illustrate a fork actuation rod and a tongueactuation rod of the invention, respectively;

FIGS. 7( a) and 7(b) illustrate a perspective view and a side view ofthe fork actuation rod having slots on both sides of the fork end;

FIGS. 7( c) and 7(d) illustrate a perspective view and a side view of anactuation rod having a slot with an open end in accordance with anotheraspect of the invention;

FIGS. 7( e) and 7(f) illustrate a perspective view and a side view of anactuation rod having a curved slot in accordance with another aspect ofthe invention;

FIGS. 8( a) and 8(b) illustrate a side view and a cross-section view ofan actuation rod having an angled slot in accordance with another aspectof the invention;

FIG. 8( c) illustrates a slot in an actuation rod having a detent orelevation shift to temporarily lock or ratchet the tips into a desiredposition in accordance with another aspect of the invention;

FIG. 8( d) illustrates a slot in an actuation rod having a lockingmechanism in accordance with another aspect of the invention;

FIG. 9 illustrates a perspective view of an assembled surgicalinstrument having a fixed tip and a mobile tip in accordance withanother aspect of the invention;

FIGS. 10( a) and 10(b) illustrate perspective views of a surgicalinstrument having an actuation rod with a vertical slot to hold afloating drive pin in accordance with another aspect of the invention;

FIG. 11 illustrates an actuation rod that is split into at least twopieces to provide independent motion to the tips in accordance withanother aspect of the invention; and

FIG. 12 illustrates an outer tube or shaft having slots to actuate thepins in the tips of a surgical instrument in accordance with anotheraspect of the invention.

DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is shown a perspective view of a laparoscopicsurgical instrument 100 of the prior art as shown in U.S. Pat. No.5,626,609, which is incorporated herein by reference. The surgicalinstrument 100 typically comprises a handle assembly 10 having a fixedhandle 12 and a pivoting handle 14. Extending from the handle assembly10 is a shaft assembly 20 comprising an outer tube 22 and an inneractuation rod 24. The actuation rod 24 slides in the outer tube 20 in acoaxial relationship. The outer tube 22 may be secured to the fixedhandle 12, while the actuation rod 24 may be secured to the pivotinghandle 14. Attached at a distal end of the shaft assembly 20 is a toolmechanism 30, which comprises of a lower jaw 32 and an upper jaw 34. Thetool mechanism 30 is connected to the shaft assembly 20 at pivot point36 through linkage mechanism 40. During use, as the actuation rod 24slides within the outer tube 22, the linkage mechanism 40 is actuated topivot jaws 32 and 34 about pivot point 36 to open and close the jaws.

Referring to FIGS. 2 and 3, there is shown a tool mechanism 30 a of theprior art which includes, for example, a first scissor blade 32 a and asecond scissor blade 34 a. In this embodiment, a housing member 50 isattached to the outer tube 22, and the tool mechanism 30 a is attachedto the housing member 50. As the handles move, the actuation rod 24slides through the outer tube 22 towards the tool mechanism 30 a. Asillustrated in FIG. 2, scissor blades 32 a, 34 a are provided with camslots 38 and 39, respectively, which slots accept a bearing post 60which is attached to inner rod 24. As the rod 24 moves, the bearing post60 slides within cam slots 38, 39 to pivot blades 32 a, 34 a about pivotpin 36 a to open and close the blades. A drawback of this tool mechanism30 a is when the blades 32 a, 34 a are open, the tail end of the bladespass through slot 70 in housing member 50 to allow the blades to open.That is, the tail end of the blades 32 a, 34 a extend out beyond theoutside diameter of the surgical instrument and look like “wings.” Thismay be a problem for the user as they can catch or interfere on tissueor other devices during use. Moreover, when the blades 32 a, 34 a areopen, the wings can stretch and deform the plastic shrink tubing that isused to insulate the shaft assembly 20. For example, this can beproblematic in that when the instrument is withdrawn from a trocar aftera procedure, the deformed tubing may not relax and it may catch on theend of the cannula, thereby pulling the trocar out of the patient.

Referring to FIGS. 4( a)-4(c), there is shown a surgical instrument 200in accordance with a first aspect of the invention having a toolmechanism 210 including a first blade or tip 212 and a second blade ortip 214, each of which has a pin 218 and 216, respectively, formed atthe proximal end. The pins 218, 216 are fixed, typically by welding, toblades or tips 212, 214 and extend outwardly of the surface of the backend of the blades or tips 212, 214. The blades or tips 212, 214 areoverlapped in a scissors configuration and are held in a pivotalrelationship with an outer tube by a common pin 220. A novel feature ofthe invention is it includes the tool mechanism 210 that interacts witha slotted actuation rod 224 as further explained below. It isappreciated that because the blades or tips 212, 214 include pins 218,216, rather than slots, much area is not needed on the back ends. Thisis beneficial because the “wingspan” of the blades or tips 212, 214 whenopened is minimized if not eliminated. In addition, the overall strengthof the blades or tips 212, 214 and the rod 224 is maximized because boththe rod and the blades are integral or are single piece components.

The fork actuation rod 224 can be formed in a number of different ways.For example, the desired features can be machined from a solid rod ortube of a desired diameter. In another aspect, a strip of metal can bestamped with the desired slots at the end, then the tube can be rolledinto a particular diameter where the slotted end can form a “fork”. Inyet another aspect, the fork features at the end of the actuation rodcan be overmolded onto a shaft to provide a cost effective component.

As to the tongue actuation rod, it can be formed in a similar way to thefork actuation rod. More specifically, machining the detail in the tipis an option as is overmolding the detail. The end of the actuation rodcan also be formed as a separate part, i.e., molded, machined, cast,MIM, etc., with the feature detail in it and then attached to a standardlength shaft by means of a thread, snap, adhesive, welding process orsome other attachment method.

Referring to FIG. 5, there is shown a perspective view of the toolmechanism 210 of FIG. 4 being connected to the actuation rod 224. It isappreciated that there are numerous methods of manufacturing the bladesor tips 212, 214. For example, the blades or tips 212, 214 can be formedfrom conventional stamping and then heat treated. In another example,the blades or tips 212, 214 can be formed from a blank of pre-hardenedmaterial and then EDM cut, waterjet cut, laser cut or even machined toobtain the final shape. It should be noted that pins 218, 216 in theback ends of the blades or tips 212, 214 can be formed directly onto theblades or pins themselves, or they can be added after the pins have beenmanufactured.

The pins 218, 216 can be locked in any one or a combination of thefollowing ways: press-fitted, swaged, threaded and/or welded. Tomanufacture the pin as part of the blades or tips 212, 214, a multitudeof processes can be used. A sheet of material can be machined to includea pivot hole as well as the pin. The sheet can then be heat treated andsent to a form grinder, which can grind one profile of the blade or tip.The ground plate can then be sent to be EDM cut and the second profilecan be cut out. This type of process can yield numbers components, withthe drive pin integrally located, with relatively low cost.

There are also additional processes that can yield the entire part froma minimum number of operations. These can include but are not limited tometal injection molding (MIM), casting, and powder metallurgy (PM). Thefinal blade can also then be sent to be sharpened or other postprocessing.

The following is a discussion of the pin and slot design of theinvention, where there are a number of advantages which can be realized.For example,

-   -   (1) The back end of each blade or tip is reduced in area so that        during full deflection, very little or no part of the blade or        tip extends beyond the outside diameter of the outer tube or        shaft. This ensures that nothing catches on the blades or tips        during grasper use and the shrink tubing found on scissors would        not be deformed. This can be done because the area for the slots        is not needed;    -   (2) The usable area for the drive slots on the blade or tip of        the actuation rod is maximized to the overall diameter of the        outer tube or shaft which provides additional leverage to the        blades or tips; and    -   (3) If channels are used on the actuation rod, the depth of the        channels can be varied such that increased tension can be placed        on the blades during actuation.

Moreover, by moving the slot from the blades or tips to the actuationrod, the “wingspan” of the blades can be reduced or eliminated becausethe back end does not need to endcase the slot, but rather a small pinwhich minimizes the chance of catching on tissue, other instruments orsuture.

Referring to FIGS. 6( a) and 6(b), there are shown the end of theactuation rod which can be a fork design 224 a or a tongue design 224 b.With the fork design 224 a, a through slot 226 can be formed on eachside of the rod 224 a. The back end of the blades or tips can beinserted into the rod where the pin of the first blade or tip can belocked into the first slot and the pin of the second blade or tip can belocked into the opposing second slot. The blades or tips can be fixed bya common pivot point on the outer tube or shaft. When the actuation rodis moved in one direction, the blades or tips will cam via the pins andthe slots 226. The pin that locks each blade or tip into the shaft canbe integral to the blades or tips or they can be separate components.Similarly to the fork design 224 a, the tongue design 224 b can includea slot 226 on each side of the tongue as further discussed below.

Referring to FIGS. 7( a) and 7(b), there are shown a perspective viewand a side view of the actuation rod 224 incorporating slots 226 on bothsides of the tongue end, respectively. As explained above, the blades ortips can have pins on the back end that nest in the slots of the rod.The rod may be pushed forward or pulled backwards to cam the blades ortips, which are pivoted by a common pivot point that is attached to theouter tube or shaft. In some cases, it is beneficial to have differentslot designs to actuate the tips to different openings, at differentspeeds, for different length tips and for varying force. Referring toFIGS. 7( c) and 7(d), the slots 226 can include an open or closed endslot (or combination of both) as desired. FIGS. 7( e) and 7(f)illustrate an actuation rod having a curved slot in accordance withanother aspect of the invention. It is appreciated that as the jawproviding the blades or tips of the invention articulates a pivot point,the distance between the pin and slot and the hinge vary depending onthe actuation rod position. Accordingly, the curved slot of theinvention can be used to compensate for this phenomenon and provide fora more linear relation between the actuation rod and the jaw motion. Forexample, the slot can be shaped to provide for more control as theblades or tips are nearing the closed position, and greater accelerationas the blades or tips are near the opened position. With this aspect,the instrument can be tuned to provide the desired instrument controland user feedback.

In another embodiment of the invention as illustrated in FIGS. 8( a) and8(b), a slot 226 b for the tongue can be formed such that it has anangle to it. In other words, the depth of the slot 226 b at one end(‘B’) 227 may be deeper or shallower than at the other end (‘A’) 228.This is beneficial because as the actuation rod 224 is pulled, and theblades or tips close, the pins camming in the slots can be forced apartby the angle at the bottom surface of the slots. This would spread theback end of the blades or tips which in turn push the front of theblades or tips together putting more tension along the cutting surface.

In yet another aspect of the invention as illustrated in FIG. 8( c),there is shown a slot 226 c having a detent or elevation shift 229 totemporarily “lock” or “ratchet” the blade or tip into a desired positionwithout affecting the linear motion of the jaws relative to the handleactuation. FIG. 8( d) illustrates that a slot 226 d can also be formedwith different cross sections, e.g., slot 226 d having a lockingmechanism with a dovetail profile 230. With this embodiment, the matingpin on the blades or tips can match the slot to “lock” it in.

In another aspect of the invention as illustrated in FIG. 9, both bladesor tips 212, 214 do not need to be mobile. That is, one blade 212 may befixed while the other blade 214 may actuate. The mobile blade 214 maycontain a pin 300 and an actuation rod 302 that would contain only oneslot to actuate the blade 214.

In yet another aspect of the invention, FIGS. 10( a) and 10(b)illustrate a surgical instrument 400 providing a floating drive pin 402in an actuation rod 410. More specifically, the actuation rod 410includes a vertical slot 404 to allow the drive pin 402 to float in.With this aspect, the drive pin 402 is positioned through slots 406, 408of blades or tips 412, 414, respectively, and is located in theactuation rod slot. An outer shaft tip 416 has a floating pin slot 418from the tip in. The floating drive pin 402 slides in this slot and iscontained therein. A pivot pin 420 is located at the tip of the shaft tolock the tip assembly in place.

Referring to FIG. 11, there is shown another aspect of the inventionwhere the slots or channels 226 can be of any of the above-describeddesign, however, the actuation rod is split into a plurality of multiplepieces 224 c, 224 d to provide independent motion to the blades or tips.This would be useful if the blades or tips need to be articulated atdifferent speeds, or over different distances.

Referring to FIG. 12, there is shown another aspect of the inventionwhere the slot or channel is located in an outer shaft 524 rather in theactuation rod. In particular, the blades or tips 512, 514 are similar tothose of the previous design, except pin 516 of blade 512, for example,extends to the outer shaft 524, which includes slots 518 to receive pins516, 520 of blades or tips 512, 514, respectively. With this aspect ofthe invention, blades or tips 512, 514 are actuated by rotating theouter shaft 524, which cause pins 516, 520 to cam along the slots 518 inthe outer shaft 524 and actuate the blades 512, 514 open and closed. Theouter shaft 524 can also be made up of multiple pieces and can include achannel rather than a through slot.

It will be understood that many other modifications can be made to thevarious disclosed embodiments without departing from the spirit andscope of the invention. For these reasons, the above description shouldnot be construed as limiting the invention, but should be interpreted asmerely exemplary of preferred embodiments.

1. A surgical instrument, comprising: an elongate tube having a centrallumen extending along an axis; an actuation rod being a two-piece forkactuation rod having a first actuation rod and a second actuation rodside by side to each other with portions of each actuation rod incontact with each other and coaxially slidable within the central lumenof the elongate tube; a first tip including a first pin formed on aproximal end surface of the first tip; and a second tip including asecond pin formed on a proximal end surface of the second tip, thesecond tip pivotally connected to the first tip at a common pivot pinoperably connected to the elongate tube to open and close the tips inresponse to movement of the actuation rod, wherein the first and secondactuation rods each have a slot to accept the respective pins of thefirst and second tips, each slot having camming surfaces for therespective pins to slide within the slot, wherein the first actuationrod and the second actuation rod are independently movable to provideindependent motion to the first tip and the second tip, wherein theproximal ends of the tips extend minimally outside the diameter of theelongate tube during actuation of the tips, and wherein the slot of thefirst actuation rod has a depth within the slot defined from an outersurface of the first actuation rod towards an inner surface of the firstactuation rod that varies along the length of the slot.
 2. The surgicalinstrument of claim 1, wherein the camming surface of and within theslot of the first actuation rod has a decreasing surface width from adistal end of the first actuation rod towards a proximal end of thefirst actuation rod to provide greater tension along the first tip.
 3. Asurgical instrument, comprising: an elongate tube extending along anaxis including an actuation rod having a first actuation rod and asecond actuation rod, the rods being independently coaxially slidablewithin the elongate tube; a first tip including a first pin formed on aproximal end surface of the first tip; and a second tip including asecond pin formed on a proximal end surface of the second tip, thesecond tip pivotally connected to the first tip at a common pivot pinand connected to the actuation rod, the first actuation rod having aslot to accept the first pin, the slot having camming surfaces for thefirst pin to slide within the slot, the slot extending along an anglethat is non-perpendicular to an axis of the first actuation rod from adistal end of the first actuation rod towards a proximal end of thefirst actuation rod and the camming surface of and within the slothaving a decreasing surface width from the distal end of the firstactuation rod towards the proximal end of the first actuation rod,wherein a distal end of the slot is enlarged.
 4. A surgical instrument,comprising: an elongate tube extending along an axis including anactuation rod having a first actuation rod and a second actuation rod,the rods being independently coaxially slidable within the elongatetube; a first tip including a first pin formed on a proximal end surfaceof the first tip; and a second tip including a second pin formed on aproximal end surface of the second tip, the second tip pivotallyconnected to the first tip at a common pivot pin and connected to theactuation rod, the first actuation rod having a slot to accept the firstpin, the slot having camming surfaces for the first pin to slide withinthe slot, the slot extending along an angle that is non-perpendicular toan axis of the first actuation rod from a distal end of the firstactuation rod towards a proximal end of the first actuation rod and thecamming surface of and within the slot having a decreasing surface widthfrom the distal end of the first actuation rod towards the proximal endof the first actuation rod, wherein a width of the slot at an outersurface of the first actuation rod is smaller than a width of the slotat an inner surface of the first actuation rod.
 5. A surgicalinstrument, comprising: an elongate tube having a central lumenextending along an axis; an actuation rod being a two-piece forkactuation rod having a first actuation rod and a second actuation rodside by side to each other with portions of each actuation rod incontact with each other and coaxially slidable within the central lumenof the elongate tube; a first tip including a first pin formed on aproximal end surface of the first tip; and a second tip including asecond pin formed on a proximal end surface of the second tip, thesecond tip pivotally connected to the first tip at a common pivot pinoperably connected to the elongate tube to open and close the tips inresponse to movement of the actuation rod, wherein, the first and secondactuation rods each having a slot to accept the respective pins of thefirst and second tips, each slot having camming surfaces for therespective pins to slide within the slot, and the proximal ends of thetips extend minimally outside the diameter of the elongate tube duringactuation of the tips, and the slot of the first actuation rod has adepth within the slot defined from an outer surface of the firstactuation rod towards an inner surface of the first actuation rod thatvaries along the length of the slot.
 6. The surgical instrument of claim5, wherein the camming surface of and within the slot of the firstactuation rod has a decreasing surface width from a distal end of thefirst actuation rod towards a proximal end of the first actuation rod toprovide greater tension along the first tip.
 7. A surgical instrument,comprising: an elongate tube extending along an axis including anactuation rod having a first actuation rod and a second actuation rod,both rods coaxially slidable within the elongate tube; a first tipincluding a first pin formed on a proximal end surface of the first tip;and a second tip including a second pin formed on a proximal end surfaceof the second tip, the second tip pivotally connected to the first tipat a common pivot pin and connected to the actuation rod, wherein, thefirst actuation rod having a slot to accept the first pin, the slothaving camming surfaces for the first pin to slide within the slot, theslot extending along an angle that is non-perpendicular to an axis ofthe first actuation rod from a distal end of the first actuation rodtowards a proximal end of the first actuation rod and the cammingsurface of and within the slot having a decreasing surface width fromthe distal end of the first actuation rod towards the proximal end ofthe first actuation rod, and a distal end of the slot is enlarged. 8.The surgical instrument of claim 7, wherein a width of the slot at anouter surface of the first actuation rod is smaller than a width of theslot at an inner surface of the first actuation rod.